Designer Adrian Newey is known for his tight-fitting cockpits, and the packaging is reportedly even more problematic for 2014 given the new turbo V6 and 'ERS' regulations.
And while Ricciardo is slightly shorter than his Australian compatriot Mark Webber, the European media reports reveal that his hips are slightly wider than Webber and world champion Sebastian Vettel's.
F1 legend Niki Lauda sees another problem with Red Bull's apparent decision to sign Ricciardo.
"Out of the new generation, Ricciardo is the driver with the most potential," the Mercedes chairman said in an interview with Bild newspaper.
"But at the moment no one knows if that potential is really enough. So it's a risk," said Lauda.
Another F1 grandee considering taking a risk for 2014 is Ferrari. According to recent reports, talks with Nico Hulkenberg about replacing Felipe Massa are underway.
"Hulkenberg is not bad," said Lauda, "but I think he needs another year. And Ferrari doesn't have time to waste."
The great Austrian said that if he was in charge at Ferrari, he would sign Kimi Raikkonen.
"He would give the team a boost, just as Lewis Hamilton has done at Mercedes," said Lauda.
"At Ferrari, Luca di Montezemolo decides alone. Alonso would certainly not like it (Raikkonen as his teammate), but Ferrari does have a problem: if the car is not good, Alonso complains all day.
"If I was Montezemolo, I would pick Kimi," he added.
Finally, Lauda said the fact Nico Rosberg has been able to keep up with Mercedes' new recruit Hamilton in 2013 was a surprise.
Asked if Hamilton's 2013 title bid has been a surprise, Lauda answered: "No, as I knew that he would give the team a boost.
"What has surprised me is that Nico has been at eye-level. Nico has had more bad luck, but as far as the speed, they're both the same," he added.